The present invention is directed to a non contacting torque sensor and specifically for a sensor that is especially useful for the steering columns of automobiles and other vehicles.
The never-ending demand for higher efficiency and higher reliability in automobiles, and the advent of the electrical vehicle (EV), have collectively doomed power hungry devices such as the Power Steering Hydraulic Pump and the Air Conditioning compressor. The best replacement for the Hydraulic Pump at this time is an electric motor to directly assist the steering effort. The problem now lies with reliably sensing the driver-applied torque so as to know how much steering assist to add. This could be accomplished with potentiometers, but the limited life of the contacting wipers is unacceptable in this very critical application. Another possibility is the use of optical encoders. While this would also perform the function, it is prohibitively expensive (especially absolute optical encoders), and the use of the light source is discouraged due to reliability considerations.
There is already known a device for sensing angular position or rotation of a steering column, as disclosed in application Ser. No. 09/390,885, filed Sep. 7, 1999 entitled Angular Position Sensor With Inductive Attenuating Coupler assigned to the present assignee and now U.S. Pat. No. 6,304,076. This patent application is hereby incorporated by reference.
It is a general object of the present invention to provide an improved torque sensor and one of the non contacting type.
In accordance with the above invention there is provided a non contacting torque sensor for a shaft having a torsion bar connecting two portions of the shaft comprising a transmit annular disk surrounding the shaft and fixed for non rotation. A pair of annular coupler disks are mounted for rotation with the shaft on opposite sides of the torsion bar. A pair of fixed receiver annular disks surround the shaft with the coupler disks between them, the pair of receiver disks receiving signals from the transmit disk through the coupler disks indicative of the rotation of the shaft. Means are provided for angularly comparing the signals from the pair of receive disks to provide a torque signal indicative of the angular differential displacement of the shaft portions.